MINE WARFARE

Interrogation of: Captain TAMURA, Kyuzo, IJN;
head of the Mine Sweeping Section of the Tokyo Ordnance Department during the war.

Interrogated by: Commander T.H. Moorer, U.S.N.

SUMMARY

Captain TAMURA answers general questions pertaining to mine warfare.
Captain TAMURA presented a paper, as previously requested which expressed the combined views of Japanese
experts on the strategical, tactical and technical aspects of aerial mining as executed by the UNITED STATES.
This paper is available under separate cover.

TRANSCRIPT

Q. Were any coast defense vessels converted into mine sweepers?
A. No, they were too large. They were used only for sweeping moored mines; however, many sub-chasers were
removed from escort duty and employed as mine sweepers.

Q. After a particular type of mine was discovered, how long would it normally take to work out and put into
effect a counter-measure?
A. The time required for each type of mine was as follows : Magnetic (needle type) -- one month, magnetic
(induction type) -- two months, acoustic (normal frequency) -- two weeks, acoustic: (low frequency) -- unable to
construct effective counter-measure but research was completed in three months, pressure type mine -- unable to
construct effective counter-measure but research completed in three months. A very few mines were swept with
net type sweepers.

Q. Did your research section make a study of underwater damage to ships caused by mines?
A. Yes. Although information was available regarding the construction of vessels, in order to protect them
against mine explosions, it was of not much use. The steel supply limited construction so that it was impossible
to incorporate new ideas in designing.

Q. What percentage of ships which struck mines were lost completely?
A. Due to the fact that mines normally were laid in shallow water, only about 50% of ships striking mines actually
sank. However, the damage is such that in deep water about 70% of these vessels would be lost.

Q. What is the general opinion of high ranking Japanese Military leaders and industrialists as to the value of
mine warfare such as executed against JAPAN?
A. During the first years of the war little importance was attached to mine warfare. However, in 1945 when
mines were used in quantity, they became of great concern to all leaders. As an example, after the use of the
pressure-magnetic mine, the problem became so acute that several military activities such as Naval Air
Headquarters even made an attempt to assist in countermeasure development, although such work did not come under
their department.

Q. Did mining effect military strategic plans at any time during the war?
A. The mine attacks in area outside of JAPAN did not effect military strategic planning. This was largely due
to the fact that the people were not aware of the extent of the allied mine effort and also were not fully cognizant
of the potentialities of mine warfare.

Q. What was the reaction of the civilian population in mined areas?
A. In view of the fact that the Japanese people were so strictly controlled and consequently did not know what
was going on, mine warfare had no effect on civilians. The only agencies that were cognizant of the critical
situation caused by the mines were the Shipping Control Board and those agencies that actually came in contact
with the results of the mine attacks.

Q. What was the date of recovery of the British type mine?
A. In June or July 1942 we found a complete mine in a warehouse in SINGAPORE.

Q. Did you discover the British magnetic acoustic mine?
A. No.

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Q. Did the Germans furnish you am counter-measure information on this mine?
A. No.

Q. Did the Japanese ever give any consideration to an offensive aerial mine campaign of their own?
A. We never had any idea of offensive aerial mining in American waters because we realized that we did not
have the planes. We did have a plan to mine OKINAWA when the campaign started but never had enough
planes to execute it.

Q. Did you capture any personnel that proved of assistance in development of mine counter-measure?
A. We never did. Captured personnel were not of as much value as the captured mine.

Q. Did you ever consider the use of barrage balloons against mine-laying aircraft?
A. No, because the material was not available.

Q. Were Area Commanders left to combat mine attacks on their own or did they receive directives and guidance
from TOKYO?
A. The Area Commanders were left to their own devices and used such equipment as was available. However
they were furnished with the latest information available at TOKYO.